Steam pressure control for directcontact heaters operating on variable pressure steam



2,636,721 ERS April 8, 1953 w. P. SPINING STEAM PRESSURE CONTROL FORDIRECT-CONTACT HEAT OPERATING ON VARIABLE PRESSURE STEAM Filed May 22,1950 AUXILIARY STEAM SUPPLY HEATER STEAM RESERVOIR TRAP FIG.I

HEATER- AUXILIARY STEAM SUPPLY AIR RESERVOIR SUPPLY INVENTOR.

G W W Dr S P N E R R A w Patented Apr. 28, 1953 UNITED STATES PATENTOFFICE Warren Pierson Spining, Livingston, N. J., assignor toWorthington Corporation, a corporation of Delaware Application May 22,1950, Serial No. 163,442

8 Claims.

This invention relates generally to direct-contact feedwater heaters,deaerators and the like, receiving their heating steam from anuncontrolled extraction source as from a steam turbine, and from whichboiler feed pumps or boiler feed booster pumps take their suction, andmore particularly to a steam pressure control system for direct-contactheaters to stabilize and maintain a sufficient head of Water therein forpumps taking their suction from these said heaters and deaerators.

In most modern central power stations such as are found in the largerpublic utility or industrial power plants and in many marine powerplants, the boiler feed pumps or boiler feed booster pumps take theirsuction from direct-contact feedwater heaters or deaerators which inturn,

receive their heating steam from an uncontrolled extraction point on themain turbine driving the generators; therefore, varies directly with theload on the main turbine, and the temperature and pressure of the steamacting on the water stored in the heater will accordingly also vary.

One of the major problems coincident with the operation ofdirect-contact heaters and deaerators on power plant extraction systemsis to insure continuous operation of the boiler feed or boiler feedbooster pumps under conditions of rapidly varying loads and steampressures. For,

whenever there is a reduction in main turbine load, with theaccompanying reduction in pressure in theheater, a portion or all of thewater stored in the heater and in the suction line connecting the pumpto the heater, will flash into steam as a result of the correspondingpressure drop in the direct-contact heater. This condition creates thepossibility of vapor binding of the pump severe enough to cause damagethereof.

The violence of this flashing and its eifect on the pump will dependupon many factors, the main ones being, the rate of pressure reductionin the heaters, the quantity of stored water in the heater, thetemperature and rate of inflow of condensate entering the heater, thedesign of the storage compartment and the static elevation of the heaterabove the pump.

In normal operation, the rate of pressure reduction can be controlledsufficiently to assure a full flow of water to the pumps, undisturbed byflashing provided the heater is located high enough above the pump toprovide a liberal margin over the net positive suction head requirementsof the pumps. However, even under these j-favorable conditions, there isalways the possi- The steam pressure in the heater,

bility that the turbine may suddenly be tripped off the line, in whichcase, in spite of all practical design precautions, the flashing may besevere enough to cause damage to the pump.

In addition, this type of installation increases building and pipingcost, and is not easily adaptable to marine installations wheresufficient net positive suction head is seldom available, and turbineload must be varied rapidly when maneuvering.

The present invention contemplates a differential steam pressure controlsystem which solves this problem by providing means for controlling therate of pressure reduction in the direct contact heater independent ofthe rate of loadreduction of the source or extraction point from whichsteam is supplied, which includes a differential pressure valve controldevice actuated by differential pressure between the steam space of theheater and a steam or air receiver, set at a pressure approximatelyequal to the instant heater pressure and adapted to be reduced slowly,whereby the. control device will allow make-up steam to be initiallyadded to the steam space in the heater and thereafter allow the pressureto be reduced slowly to prevent undue flashing.

Accordingly, it is an object of the present invention to provide adiiferential pressure control system for direct-contact heaters whichwill assure a constant head of water on the boiler feed or booster pumpstaking their suction therefrom,

undisturbed by violent flashing conditions, re-

gardless of the changes in pressures of the source supplying steam tothe direct-contact heater.

It is another object of the present invention to provide a steampressure control system for direct contact heaters which will permit asubstantial reduction in elevation of the heater above the pump withoutsacrificing operating reliability.

With these and other objects in view, as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing a steam pressurecontrol for direct-contact heaters operating on vari able pressure steamof a preferred form embodying the invention, and the features formingthe invention will be specifically pointed out in the claims.

In the drawings- Figure 1 is a diagrammatic sketch showing theinvention.

Figure 2 is a diagrammatic sketch of a modified form of the invention.

Figure 3 shows one type of valve which may be used with the invention.

Referring to the drawings, Figure 1 shows a diagrammatic sketch of thecontrol system connected to a direct-contact heater i, which may be anysuitable type of feedwater heater, deaerator or the like type ofdirect-contact heater, of which there are several easily purchasable onthe open market.

The direct-contact heater i, has a steam receiving space 22 and a waterstorage space Inlet means l for water is mounted in the heater to admitsaid incoming water into the steam receiving space for direct-contactwith the steam being supplied through conduit from some uncontrolled andvariable pressure steam source such as an extraction outlet on the mainturbine (not shown) of a power plant, whereby the steam will act as aheating medium for the incoming water. Conduit provided with a checkvalve ii O that when steam pressure at thesource is less than the steampressure in the steam receiving space 2 the steam will be prevented frompassing back to the source by the check valve.

A boiler feed pump or boiler feed booster pump i is connected to thewater storage space 3 by means of suction line 8, and accordingly willtalre itssuction from the water storage space.

In order to maintain a constant head of water on the pump, when suddenreduction in pressure occurs in the steam receivingspace 2, an auxiliarysteam supply from some fixed source .Sllh as a main boiler (not shown)is connected to the steam receiving space 2 by means of auxiliary steamsupply conduit 9.

The quantity of steam from such abovernentioned auxiliary steam supplydelivered to the steam receiving space is determined by the differentialpressure between the steam receiving space 2 and a pressure or steamreservoir I0 through the medium of a balanced pressure actuated valve ll interposed in the auxiliarysteam supply conduit 9.

The pressure actuated valve l I in the preferred form is indicated inFigure 3 as a balanced diaphragm type valve, it beingunderstood'however, that while this type of valve is shown that anyother suitable type of valve may be utilized .for this purpose.

Thus, referring to Figure 3, the pressure actuated valve is shown insection comprising a valve housing it having the valves l3 positionedtherein to control the fiow of steam through the valve housing andconsequently through the steam supply pipe 9. Connected to the valves 53is an elongated valve stem Hi which extends upwardly from the valvehousing l2, through the valve guide structures it: and it into a sealedchamber ll mounted on the valve housing where it is fixedly connectedfor movement with 2. diaphragm member l8 lying substantially in themedial plane of said chamber 18 to divide it into an inner chamber isand an outer chamber 2t. Suitable packing structures 26 and 22 areprovided about the valve stem where it passes out of said valve housing52 and into said valve chamber 2b to prevent steam from leaking toatmosphere.

The diaphragm member 18 is of the balanced type so that as it is movedinwardly and outwardly responsive to steam pressure as hereinafterdescribed, the valve stem will cause the valves is to open and close tocontrol the flow of steam in the auxiliary steam supply conduit 9 to thesteam receiving space.

A resilient member 23, is adjustably mounted about the valve stem and isadapted to abut a stop member M, for normally urging the valves it intoa closed position. Thus, the total effect across the diaphragm as to theamount it will open over and above this spring member will depend on thebalance of pressure between the inner chamber i9 and outer chamber 25].

The means for actuating the diaphragm i8 and thus controlling the actionof the valves, also acts to control the rate of pressure reduction inthe direct-contact heater, as shown in Figure 1.

Thus, steam reservoir it, which may be any suitable type of wellinsulated steam reservoir easily purchasable on the open market, willreceive steam therein through a connecting conduit 25 leading from thesteam receiving space 2 of the direct-contact heater, whereby steam atsubstantially the same or slightly lower pressure will be present in thesteam reservoir it. .A check valve as is provided in connecting conduit25 to prevent any flow of steam from the reservoir to the direct-contactheater when the pressure is reduced in the direct-contact heater.

A small orifice or needle valve 2? is provided on the steam reservoir 18, to permit the constant escape of a smail predetermined amount ofsteam to atmosphere causing the steam pressure in the steam reservoir tobe maintained slightly lower than the steam pressure in the heaterduring normal operation, and to allow the steam pressure in the steamreservoir'to fall at a fixed or predetermined rate whenever heaterpressure is less than reservoir pressure. kfiheclr valve '26 will closeto prevent the steam from passing back along the connecting conduit '25whenever the pressure in the heater reduces below the pressure in thesteam reservoir iii.

A trap 28 is also provided in the steam reservoir to remove anycondensate which forms therein, and to provide means for returning itthrough return conduit'iii to the water storage space 3 of thedirect-contact heater 5, all of the above being clearly shown in Figurel of the drawings.

Between the check valve 26, and the steam receiving space 2, an inletpipe 3&3 joins the connecting conduit 25 and the outer chamber 2twhereby steam at substantially heater pressure will be acting in outerchamber 28 on one side of the diaphragm member l8.

Between check valve 26 and the steamreservoir it, a second inlet pipe 3!joins'the connecting conduit 25 and the inner chamber ii! whereby steamat substantially the same pressure as the steam in the connectingconduit and the steam reservoir will be acting in inner chamber [9 onthe other side of the diaphragm member I 8, all of which is clearlyshown in Figures 1 and 3 of the drawings.

Under normal operating conditions, steam will be delivered to the heateri from the source point or extraction point on the main turbine (notshown). As long as the load operation of the turbine is constant or thesupply of steam is delivered at a constant pressure, the pressure in theheater i will be substantially the same or slightly higher than thepressure in the reservoir Hi. Accordingly, the pressure acting in theouter chamber 29 combined with the pressure exerted by the spring member23 will keep the valves it closed. No make-up steam is needed andaccordingly none is delivered.

However, when the turbine extraction steam pressure is reduced or thesupplied steam entering through conduit 5 is reduced, heater pressurewill also reduce. Check valve 6 will close to prevent steam flowing backthrough conduit 5. Check valve 26 will close to prevent any steam fromflowing back to the steam receiving space 2 and accordingly the pressureacting in inner chamber l9 will be greater than the pressure acting inouter chamber 20 combined with the pressure, exerted by the springmember 23 and the valves It will be opened to allow make-up steam topass through the auxiliary steam supply pipe 8 to the steam receivingspace 2, until the pressure in the steam receiving space 2 builds up thepressure sufficiently to prevent flashing of the water in the waterstorage space 3 of the heater I. Since, however, steam will be escapingfrom the reservoir H1, at a predetermined fixed rate, the pressure inthe reservoir ||l will gradually fall, until the pressure in the steamreceiving space '2 will be equal to the pressure being supplied from theextraction point of the turbine (not shown) or some other source inwhich case the pressure differential across valve diminishes and thevalve closes. Then check valve 6 will open to allow steam once again to.be supplied at the new reduced pressure to the heater. The total actionof valve when a reduction in pressure occurs is to maintain a pressurein the heater equal to that in the reservoir l0. Since, however, therate of pressure drop in the reservoir Hi can be controlled byadjustment of the needle valve or selection of the orifice size, itfollows that the rate of pressure reduction in the direct contact heateris likewise controlled.

In some cases, it may be desirable to utilize an air reservoir in placeof the steam reservoir for establishing a fixed rate of pressure drop.This modified type of system is illustrated in Figure 2 of the drawings.

Referring therefor to the drawings, Figure 2 shows a direct-contactheater I having a steam receiving space 2 and a water storage space 3'.Inlet means 4 for incoming water is mounted in the heater to admit saidwater into the steam receiving space 2' for direct-contact with thesteam being supplied to the steam receiving space by conduit 5'connected thereto from some uncontrolled steam source such as anextraction outlet on the main turbine (not shown) of a power plantwhereby the steam acts as a heating medium for the incoming raw water.Conduit 5' is provided with a check valve 6. A boiler feed pump orboiler feed booster pump is connected by a suction line 8' similarly asdescribed above.

The quantity of steam delivered to the steam receiving space 2 from theauxiliary steam supply (not shown) by means of auxiliary steam supplyconduit 9 is determined by the differential pressure between the steamreceiving space 2' and an air reservoir I0 through the medium of abalance pressure actuated valve interposed in the auxiliary steam supplyconduit 9', all of which is clearly shown in Figure 2 of the drawings.

The valve II is identical with that above described, and accordingly isidentical with valve shown in Figure 3 of the drawings.

The means for actuating the diaphragm in valve H, in the modified formwill depend on the differential pressure between pressure in the airreservoir 1' and the steam pressure in the steam receiving space and themeans for reducing the pressure will be incorporated in the airreservoir ID in similar fashion as hereinafter described.

Air reservoir I0, is substantially cylindrical in construction and maybe any suitable type of air receiver of which there are many well knownin the compressor art. It is supplied with air under pressure from somesuitable source (not shown) through air supply conduit 4|). Abalanced-diaphragm type valve 4| is interposed in the air supply conduit40 to control the flow of air under pressure to the air reservoir I0.

Valve 4| is substantially identical with valve shown in Figure 3.

Valve 4|, is actuated by steam under heater pressure delivered to oneside of the diaphragm by a steam connecting conduit 42 connected betweenthe steam receiving space 2' and valve 4|, and on theother side of thediaphragm by an air conduit 43 connected between the air reservoir H3and the valve 4| which delivers air under reservoir pressure to saidother side of the diaphragm. Air at reservoir pressure will tend toclose the valve 4| and steam at heater pressure will tend to open it.The total effect with the spring member maintaining the valve normallyclosed will be that the relative amount that the valve opens will be afunction of the differential pressure between the heater and thereservoir Ill.

Thus, as the pressure in the heater falls below that in the reservoir,the air pressure acting on the diaphragm in valve 4| will act to closeit.

Since the pressure in the air reservoir In will actuate valve thedifferential pressure is also established by the pressure of the steamin the heater and the air under pressure in the air reservoir HIT, assteam under heater pressure will be delivered to valve through inletpipe 30' connected to conduit 42 to act in outer chamber 2i) on one sideof the diaphragm, and air under pressure will be supplied through asecond inlet pipe 3| connected between the air reservoir It and innerchamber H! to act on the other side of the diaphragm.

The air reservoir Ill similarly to the above described steam reservoir|0, is also provided with an adjustable needle valve or properly sizedorifice 44, to allow the pressure therein to be reduced at a constantrate. Thus, since valve maintains heater pressure approximately equal toreservoir pressure, means is provided to positively control the pressuredrop in the direct contact heater where reduction of pressure from theuncontrolled extraction point on the turbine (not shown) or uncontrolledand variable pressure source occurs.

In the operation of the modified form, when the pressure is reduced inthe direct-contact heater I, check valve 6 closes. The pressurein theair reservoir I0 acts simultaneously to close valve 4| to stop thesupply of air under pressure to the air reservoir, and to open valve Hto allow make-up steam to enter through auxiliary steam supply conduit9' to the steam receiving space.

Since the adjustable needle valve 44 will allow the pressure in the airreservoir Ml to reduce at a predetermined controlled rate, pressure inthe steam receiving space 2 will slowly reduce to the new lower pressureat which point equilibrium of pressure across the diaphragm of valve Hwill allow it to close and similar equilibrium of pressure across thediaphragm of valve 4| will allow it to open so that air under pressuremay be supplied to the air reservoirs by a supply conduit 40 once again.

In either form of this invention it appears obvious that when steam issupplied at an increased pressure, the problem of flashing will notarise.

It will be understood that the invention is not to be limitedpto thespecific construction or at'- rangement of parts shown but that they maybe Widely modified within the invention defined by the-claims.

What is claimed is:

1. In a differential pressure control and reduct-ion system for directcontact heaters receiv ing a main source of steam :atvariable pressurein the steam receiving space thereof, an auxiliary steam supply conduitconnected to supply make-up steam thereto-a valve inaintainedncrmailyclosedconnected in said steam supply conduit for controlling the flow ofmake-up steam from said auxiliary steam supply to said steam receivingspace, a balanced diaphragm means connected to said valve for open ngsaid valve responsive to differential pressure across said diaphragm,asteam reservoir, 2, connecting conduit be" seen said reservoir and thesteam receiving space to supply steam to the reservoir at substantiallythe same pressure as the steam supplied to steazn'receiving space, acheck valve in said-connecting conduit to prevent back. flow or steamwhen thepressureinsai-d steam re-- ceiving space is less than in thesteam reservoir, conduit-means connecting the steam reservoir and thesteam receiving to opposite sides of said diaphragm to actuate saiddiaphragm by the differential pressure between said steam resetoir andsaid steam receiving space, and adjustable means on "said steamreservoir positioned'to reduce the pressure in steam reservoir tocontrol the rate of pressure reduction in said steam receiving-spaceirrespective of the reduction of pressure of the variable pressure steamsupplied to the steam recei rig-space.

2. In a differential control and reduction system for direct contactheaters claimed in claim 1 wherein said adjustable means on the steamreservoir includes, an august-able needle valve mounted onthesteanrreservoir set'to allow a predetermined quantity of steam toescape to atmosphere from said steam reservoir.

3. In a dilierential control and reduction sys tem for direct contactheaters as claimed in claim 1 wherein means are provided for returningcondoused steam from the steam reservoir to the contact heater includinga trap connected to the lower portion of said steam eservoir to receivecondensate therein, are n conduit connected between the trap and the.ect contact heater to return the-condensate 'fromthe trap to theheater.

4. 111 a difierential pressure control and reductionsystem for directcontact heaters recei ing main source of steam at variable pressure inthesteam receiving space thereof, an auxiliary steam supply conduitconnected to said steam receiving space, a first valve maintainednormally closed connected in said steam supply conduit for controllingthe flow of make-up steam from said auxiliary steam supply to said steamreceiving space, a balanced diaphragm connected to said valve foropening said valve responsive to differential pressure across saiddiaphragm, a pressure reservoir, means connecting the pressure reservoirand the steam receiving space tosaid balanced diaphragm to actuate saiddiaphragm by the differential pressure between said pressure reservoirandsaid steam receiving space when the pressure of the main source ofsteam supplied to the direct contact heater is reduced, means includinga line for supplying pressure medium to said pressure reservoir, asecond valve in said line maintained normally open to regulate theamount of pressuresupplied to said pressure reservoir, a second balanceddiaphragm connected to said second valve for closing said second valveresponsive to differential pressure across said second diaphragm, meansconnectin said pressure reservoir and said steam receiving space to saidsecond balanced diaphragm to actuate said second diaphragm for closingthe second valve to maintain the pressure reservoir at a pressuresubstantially equal to the pressure in said steam receiving space, andadjustable means on said pressure reservoir positioned to reduce thepressure in said pressure reservoir at a predetermined rate to contolthe rate of pressure reduction in the steam receiving spaceirrespectiveof the reduction in-pressure of the steam being suppliedLbY the mainsource to the steam receivin space.

5. In a differential control and reduction systern for direct contactheaters as claimed in claim l wherein said adjustable means on thepressure reservoir includes, an adjustable needle valve inounted-onthesteam reservoir set-to allow a predetermined quantity of the pressuremedium to escape to atmosphere from said pressure eservoir.

in a difierential pressure control and reduction system for dir ctcontact heaters receivin a main source of steam 'at'variable pressuresteam receiving space thereof, valve means :orniaily closed forcontrolling a supply of makeo from an auxiliary steam-source to saidsteam receiving space, a pressure reservoir operatively connected tosaid steam receiving space, conduitmeans connecting saidvalve means withpressure reservoir and said steam-receivspace for controlling andactuating said valve means by the difierential pressure between saidpressure reservoir and said steam receiving space, and bleed -off meanson said-pressure reservoir to control the rate of reduction in pressurein said pressure reservoir and in said steam receiving space operativelyconnected therewith irrespective of the reduction in pressure of thesteam supplied'to said steam receiving space from said inainsource.

7. In a differential pressure control and reduction system for directcontact heaters receiving a'main source of steam at variable pressure inthe steam receiving space thereof, an auxiliary steam supply connectedto said steam receiving space, at least one difierential pressureoperated valve means in said auxiliary steam supply maintained normallyclosed, a reservoir, means to operatively connect said reservoir to thesteam receiving space, insane for maintaining the pressure in said.reservoir at a pressure substantially equal to the pressure of the-steamsupplied to said steam receiving space during normal operation, conduitmeans connecting said valve means With said reservoir and said steamreceiving space whereby said valve means-is controlled and actuated bythe diflierential pressure between said reservoir and said steamreceiving space when the pressure of said-main source of steam enteringsaid steam receiving space 'is;reduced, and bleed-off means on saidpressure reservoir to control the rate of reduction of pressure in saidreservoir and in said steam receiving space operatively connectedthereto irrespective of the reduction in pressure of the steam suppliedto said steam receiving space from said main source.

8.,In a differential pressure control and reduction system for directcontactheaters receiving a main source of supply at variable pressure inthe steam receiving space thereof, an auxiliary steam supply connectedto said steam receiving space, at least one differential pressureoperated valve means in said auxiliary steam supply maintained normallyclosed, a pressure reservoir, means for maintaining the pressure in saidpressure reservoir at a pressure substantially equal to the pressure ofthe steam supplied to said steam receiving space, a check valve in saidmeans to prevent back flow of pressure medium from said pressurereservoir to said steam receiving space, conduit means connecting saidvalve means with said pressure reservoir and said steam receiving spacewhereby said valve means is controlled and actuated by the differentialpressure between said pressure reservoir and said steam receiving spacewhen the pressure of said main source of steam entering the steamreceiving space is reduced, and bleed-off means on 0 said pressurereservoir to control the rate of reduction in pressure in said reservoirirrespective of the reduction in pressure of the steam supplied to saidsteam receiving space from the main source.

WARREN PIERSON SPINING.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 642,088 Deems Jan. 30', 1900 2,029,505 Rawson Feb. 4, 19362,085,782 Blanchard July 6, 1937 2,372,087 Karassik Mar. 20, 19452,489,345 Welch Nov. 29, 1949 FOREIGN PATENTS Number Country Date307,266 Germany Aug. 12, 1918 387,584 Germany Jan. 4, 1921

